Release mechanism for ratchet-type power unit

ABSTRACT

Release mechanism for a ratchet-type power unit utilizing a ratchet drum upon which a flexible tension member is wound. Rotation of the drum is produced by oscillation of a lever arm having a ratchet catch pivotally mounted thereon. The release mechanism of the invention permits pivoting of the catch between a drum engaging ratcheting position, and an untensioning or &#39;&#39;&#39;&#39;let down&#39;&#39;&#39;&#39; position where the catch clears the ratchet teeth of the drum. The catch includes a torsion spring exerting a constant biasing force thereon about the catch pivot, and a leaf spring mounted on the catch is selectively engageable with a movable spring compressor which selectively permits the leaf spring to overcome the torsion spring bearing force. The spring compressor is mounted upon a slidable carriage for accessible manual operation and positioning, and the catch includes a manually operable portion disposed adjacent the spring compressor carriage.

Unite States Patet 91 Cain [ 1 Apr. 17, 1973 RELEASE NIECHANISM FORRATCI-ET-TYPE POWER UNIT [75] Inventor: Robert L. Cain, West Lafayette,

Ind.

' [73] Assignee: The American Gage 8: Manufacturing (30., Wauseon, Ohio[22] Filed: LMar. 10, 1971 H [21] Appl. N02 122,755

52 us. ca. ..254/l64, 254/167, 74/149 51' Int. Cl. ..A63b 61/04 [58],Field of Search ..254/l64, 167; p 7 74/149, 154

[56.15. 1 References Cited v UNITED STATES PATENTS 3,003,359 10/1961Maas dam ..254/l67 X 512,908 1/1894 Scheer ..74/ 149 X 2,507,889 5/1950Coffing ..74/154 X Primary Examiner-Evon C. Blunk AssistantExaminer-Merle F. Mafi'ei AttorneyBeama.n & Beaman Release mechanism fora ratchet-type power unit utilizing a ratchet drum upon which a flexibletension member is wound. Rotation of the drum is produced by oscillationof a lever arm having a ratchet catch pivotally mounted thereon. Therelease mechanism of the invention permits pivoting of the catch betweena drum engaging ratcheting position, and an untensioning or let downposition where the. catch clears the ratchet teeth of the drum. Thecatch includes a torsion spring exerting a constant biasing forcethereon about the catch pivot, and a leaf spring mounted on the catch isselectively engageable with a movable spring compressor whichselectively permits the leaf spring to overcome the torsion springbearing force. The spring compressor is mounted upon a slidable carriagefor accessible manual operation and positioning, and the catch includesa manually operable portion disposed adjacent the spring compressorcarriage.

10 C, 6 Drawing Figures PATENTED APR 1 H975 SHEET 1 [1F 2 INVENTORROBERT 4 CAIN ATTORNEYS PATENTEDAPR 1 H915 3'. 727. 886

SHEET 2 BF 2 INVENTOR ROBERT L. ,Gfldfi ATTORNEYS RELEASEMECHANISM FORRATCHET-TYPE murowsauurr I BACKGROUND OF THE INVENTION The inventionpertains to power units of the ratchet V The'spring compiressor memberis mounted upon a which is of the manually operated type and maybe usedfor lifting, stretching, bracing, pulling, or other'applications whereinit is desired to produce a tension force. Such power units have foundwide applications of use and may be used to raise or lower loads,stretch fence, tighten guy wires, pull stumps, tie down cargo, orsimilar applications. I

Basically, such power units include a frame upon which a ratchet drum isrotatably supported, the drum including a member having ratchet teethconcentrically formed thereon. The tension member, such as a rope, chainor cable, is wound on the drum, and the frame in- 'cludes a pawl whichprevents rotation of the drum in the unreeling or unwinding direction. Alever arm is mounted upon the frame for pivotal oscillation about thedrum axis,-and a catch mounted on the lever arm engages the drum ratchetteeth to producedrum rotation in a winding or tensioning direction.Thecatch of the lever arm engages the ratchet teeth during tensioning,and when it is desired to release the tension the catch is positioned soas not to engage the drum ratchet teeth, but may function to cooperatewith the pawl to permit a tooth by tooth release of the drum in anindexing manner to remove the cable tension. Such av structuralrelationship, and operation, is disclosed in US. Pat. No. 2,50l,2 53.

While the structure of the aforementioned patent permits an operablepower unit to be produced, im-

provements in the catch release positioning apparatus SUMMARY OF THEINVENTION It is an object of the invention to provide'a releasemechanism for ratchet-type power unit catches wherein the mechanism isof an economical, readily manufacturable nature, easily operated byusers of conve'ntional skill, self-indicating with respect to thecondition of the release mechanism, and capable of manual operation inorder to produce a versatility of lever arm movement and action andpermit operation in the event ofa catch spring failure.

In the practice of the invention the catch forthe drum ratchet includesa hub having an extending finger adapted to engage the drum ratchetteeth. Additionally, an extension radially projects from the hub forpermitting manual operation of the catch. A releasing leaf spring isaffixed to the catch in a mannerwhich minimizes the likelihood of springbreakage, and the leaf spring includes a free end adapted to beselectively engageable by a movable spring compressor member mountedupon the lever arm.

carriage or slide linearly movable on the lever arm. Compression of thefree end of the leaf spring overcomes the biasing force normally imposedon the catch by a torsion spring tending to engage the catch with thedrum ratchet teeth and, the positioning of the slide and springcompressor determines whether the catch is in a release or drum windingcondition.

The spring compressor and leaf spring are effective to maintain thecatch in the release position, yet the biasing force exerted on thecatch by the leaf spring x'may be overcome by engagement with the pawlduring the hoist untensioning or letdown operation.

The extension defined on the catch extends from the lever handleadjacent the spring compressor carriage and the condition of the catchmay be manually changed without utilizing the spring compressor, ifdesired. However, normal operation of the release mechanism entails useof the spring compressor and leaf spring mounted upon the catch.

In order to reduce the likelihood of spring breakage of the catchrelease mechanism, the leaf spring associated with the catch is anchoredto the underside of the catch extension remote from the catch hub. Theleaf spring then passes about the hub through an are greater than and adepression is defined in the spring adjacent the hub for permittingclearance between the spring compressor and leaf spring. The outermostfree end of the spring extends toward a guide plate mounted upon thelever arm in which a slot is defined which slidably receives the springcompressor carriage and the free end of the spring extends toward thisslot for selective engagement by the spring compressor. This manner ofsupporting the leaf spring prevents a localized high stress bendinglocation from occurring within the leaf spring, resulting in extendingthe spring life.

It is therefore one of the basic objects of the inven- I tion to providea release mechanism for aratchet-type power unit which is economical tomanufacure, positive in operation. and readily adjustable by theunskilled, while providing an improved versatility of operation.

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects andadvantages of the invention will be apparent from the followingdescription and accompanying drawings wherein:

FIG. I is a side elevational view of a power unit constructed in accordwith the invention illustrating the lever-arm at the beginning of apower stroke for winding of the tension member on the drum,

FIG. 2 is enlarged, detail, plan view of the drum, catch mechanism, andpawl as taken from the top of FIG. 1,

FIG. 3 is an enlarged, detail, partially sectioned, side elevationalview of the lever arm and catch structure illustrating the structure inthe catch release position,

FIG. 4 is a detail, sectional view of the catch structure similar tothat shown in FIG. 3, illustrating the components in the tensioning orwinding condition,

FIG. 5 is a top, enlarged, detail view of the catch, the guide platebeing broken away for purpose of illustration, and

FIG. 6 is an elevational, sectional view taken through the catchextension and leaf spring fastening means along Section 6.6 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The basic relationship ofcomponents constituting a power unit of the type with which the improvedrelease mechanism is employed will be appreciated from FIGS. 1 and 2.The power unit includes a frame formed by a pair of elongated strapmembers maintained in spaced parallel relationship at their centralregion by bolts 12 and 14 inserted through spacer sleeves, not shown.The end regions of the members 10 are deformed toward each other as at16, FIG. 2 wherein the ends of the members may contiguously be connectedby a bolt 18, at one end, to which the hook and swivel fitting 22 areattached. At the other end of the frame the ends of the members 10 aremaintained in contiguous relationship by a bolt 24 which also serves tomount the tension member guide 26 upon the frame.

The ratchet drum 28 is rotatably mounted upon the frame central regionby axle bolt 30 extending across the frame members 10, and the drumincludes a circular end plate 32, and an end plate 34 upon which ratchetteeth 36 are concentrically formed about bolt 30. The flexible tensionmember, such as the cable 38, is wound upon the drum 28 and extendsthrought the U-shaped guide 26 terminating in a hook 40, FIG. 1.

The rear side of the ratchet drum 28 is preferably encased by a shield41 of sheet metal which is mounted on the frame members 10 by smallrivet pins 43. The shield protects the drum 28, particularly when thepower unit is located near the ground or other surface.

Rotation of the drum 28 is accomplished by the lever arm 42 pivotallymounted to the frame for oscillation about the drum axle bolt 30. In thedescribed embodiment the lever arm is in the form of a cylindrical tubehaving a synthetic plastic handgrip 44 attached at the outer end and thehandle is split and bifurcated at 46 to form a pair of flattened straps48 which are bent parallel to each other adjacent their inner endregions for embracing the ratchet drum 28 and are pivotally connected tothe drum axle bolt 30.

Rotation of the ratchet drum 28 in the unreeling or untensioningdirection, i.e., counterclockwise, FIG. 1, is prevented by the pawl 50pivotally mounted upon the spacer sleeve of the bolt 12. The pawlincludes a finger portion 52 which engages a drum ratchet tooth toprevent counterclockwise drum rotation, and torsion spring 54 disposedabout the pawl hub maintains a biasing force on the pawl, clockwise whenviewed in FIG. 1, for maintaining the pawl finger in engagement with aratchet tooth 36, one end of the torsion spring being connected to thepawl, while the spring end 56 is affixed to a frame member 10. The pawl50 also includes a resiliently mounted abutment 58 on the finger 52 andAs described above, the bifurcated end of the lever arm 42 includesstraps 48 and the spacing between these straps is maintained by a spacersleeve 60 mounted upon a bolt 62 engaging the inner surfaces of thelever arm straps, and the catch 64 is mounted for pivotal movement uponthe spacer sleeve 60.

The configuration of the catch 64 is best appreciated from FIGS. 3through 5. The catch is preferably formed of a cast metal and includesan elongated hub 66 of a generally cylindrical configuration. The hub isaxially bored at 68 to receive the spacer sleeve 60 and a finger 70 ishomogeneously defined on the hub and extends therefrom in asubstantially radial direction. The finger 70 is provided with anabutment surface 72 at its outer end which is adapted to conform to, andengage with the drum ratchet teeth 36 when interconnection between thelever arm and ratchet drum is desired.

An extension 74 is also homogeneously defined on the hub 66 and extendsfrom the central region thereof in a radial direction away from thefinger 70. The extension 74 includes oppositely disposed sides 76 and78, and is of an arcuate configuration terminating at its free end in aflattened portion 80 which extends from between the lever arm straps 48for accessibility by the operator. The accessibility of the extensionportion 80 permits manual operation of the catch, and its locationadjacent the catch release mechanism further contributes toward theversatility and convenience of the release mechanism.

The catch is continuously biased in a clockwise direction, FIGS. 3 and4, about the bolt 62 by a torsion spring 82 circumscribing the hub 66and including a free end 84 hooked about the extension side 78, whilethe other spring end 86 is connected to the lever arm by the lancedanchor 88. This clockwise biasing of the catch tends to maintain thefinger abutment surface 72 in engagement with the drum ratchet teeth 36,and engagement of the finger with the ratchet teeth will limit theclockwise catch pivotal displacement.

When unreeling or untensioning the tension member it is desired that thecatch 64 be released from the ratchet teeth whereby pivoting of thelever arm will not produce a rotation of the ratchet drum. The releaseposition of the catch is illustrated in FIG. 3 wherein the fingerabutment surface 72 is radially located from the drum axle bolt 30sufficiently to clear the drum ratchet teeth 36. Of course, in order tomaintain the catch in the release position of FIG. 3 it is necessary toovercome the biasing force continuously imposed on the catch by thetorsion spring 82 and the torsion spring biasing force is overcome bymeans of a second biasing force imposed on the catch tending to producerotation of the catch in a counterclockwise direction, FIG. 3, and thesecond biasing force is of a greater magnitude than that produced by thetorsion spring.

The release biasing force is imposed on the catch 64 by a leaf spring 90mounted on the catch. The leaf spring 90 is of a width substantiallyequal to the width of the extension 74 and is formed of spring steel.The anchored end 92 of the leaf spring is affixed to the abutment side78 by a rivet pin 94 pressed into a hole 96, FIG. 6, drilled into theextension. The leaf spring then extends toward the hub 66 and passesabout the catch hub in an arc slightly greater than It will be notedfrom the drawings that the portion of the leaf spring extending aboutthe catch hub is closely received on the catch hub, and a depression 98is defined in the spring free end upon leaving the hub. The free end ofthe leaf spring is now disposed adjacent the extension side 76, and theoutermost end 1110 of the leaf spring extends away from the extensionside 76 to the position shown in FIG. 4, when the leaf spring compressoris in the inactive position.

The selective control of the biasing force imposed upon the catch 64 bythe leaf spring 911 is produced by control means mounted upon the leverarm 42. This control means includes a guide plate 102 extending acrossthe lever arm bifurcation straps 48 and having tab extensions 104extending to the catch bolt 62 as to be affixed thereto by holes, notshown, defined in the tabs through which the bolt extends. Also, smallertabs 106 extend from the guide plate 102 and are attached to the leverarm straps 48 by small rivets 108, FIGS. 1 and 2.

The flat guide plate 102 is centrally provided with an elongated slot110 disposed parallel to the longitudinal length of the power unit, anddisposed immediately above the free end of the leaf spring 90. Acarriage or slide 112 is slidably received within the plate slot 110 andincludes a button or manually engaging portion 114 disposed adjacent theplate side 1116. On the underside of the plate, adjacent the plate side118, the carraige includes a spring compressor abutment 120 whichextends from the carriage toward the leaf spring 90. The carriage 112may be formed of a plastic material wherein both the button 114 and thespring compressor 121) are nonmetallic. The carriage includes a narrowneck 122, FIG. 4, slidably received within the slot 110 interconnectingthe button and carriage and as the dimensions of the button and springcompressor are greater than the slot, the carriage will be retained inthe slot shiftable between the slot ends as apparent in,

FIGS. 3 and 4.

When the carriage or slide 112 is in the position of FIG. 4 the springcompressor 121) is disposed opposite the spring depression 28, and istherefore out of engagement with the leaf spring 90. In this positionthe only biasing force imposed upon the catch 64 is that produced by thetorsion spring 82, which will produce engagement between the catchfinger 76 and the drum ratchet teeth 36 to transfer rotation of thelever arm 42 to the ratchet drum and tension the cable 38 uponoscillation of the lever arm. This position of the carriage 112 isindicated as the up position by indicia located on the guide platesurface 116, FIG. 2. Under these conditions, it will be noted, FIG. 4,that the leaf spring free end 100 only lightly engages the underside 118of the guide plate 102, and the biasing force on the catch in acounterclockwise direction produced by this engagement of the leafspring 911 and the guide plate is insufficient to overcome the torsionspring 62.

When it is desired to pivot the catch 64 to the release position of FIG.3, thecarriage 112 is moved in the slot 110 to the position shown inFIG. 31 designated the down condition by the indicia formed on the guideplate surface 116. Movement of the carriage from the position of FIG. 4to that of FIG. 3 causes the spring compressor 120 of the carriage toengage the spring free end portion 1116 and bias the spring outer freeend away from the guide plate 102 toward the extension 74. Thisdeformation of the leaf spring 90 produces a biasing force on the catch64 in a counterclockwise direction greater than the clockwise biasingforce produced by the torsion spring 82. Thus, the catch will be rotatedin the counterclockwise direction, FIG. 3, to the position as shownwherein the finger abutment surface '72 is out of alignment with, andclears the ratchet teeth 36.

In the release position shown in FIG. 3 the lever arm 42 may be pivotedabout the drum axle bolt 30 without producing rotation of the ratchetdrum. Movement of the lever arm to its maximum extent in a clockwisedirection, FIG. 1, causes the catch finger 711 to engage the releaseabutment 58 defined on the pawl 50 lifting the pawl from the engagedratchet tooth, and the engagement of the release abutment 58 with thepawl simultaneously produces a force on the catch finger toward theratchet teeth 36 to overcome the biasing force of the leaf spring 9% andthereby align the finger surface '72 with the ratchet teeth so as toengage a ratchet tooth when the pawl 50 is released from its associatedtooth. Thereupon, the lever arm is moved several degrees in acounterclockwise direction, FIG. 1 away from the pawl which permits thepawl to again align with a ratchet tooth 36 and upon engagement with analigned tooth release the force being imposed upon the catch, and permitthe leaf spring to pivot the catch out of alignment with the ratchetteeth. Movement of the lever arm again toward the pawl 50 repeats theaforedescribed releasing or untensioning-of a ratchet drum 2%, and theratchet drum is able to index in a tooth by tooth manner to unwind thetension member 38 and remove the tension therefrom. This type of catchand pawl operation is known in the art and described in US. Pat. No.2,501,253.

The catch extension portion 86 is disposed adjacent the guide plate1112, and the operator is able to manually position the catch 64 bymeans of the extension end portion. During normal operation, such manualcatch operation is not required. However, should the operator desire tomanually lift the catch from the ratchet teeth when the carriage 112 isin the up position during return movement of the lever arm the operatormay manually depress the extension portion 811 during the lever armreturn stroke. Furthermore, during release of the pawl the operator maydesire to sense the position of the catch with his finger, and this maybe accomplished through the extension portion 86. The extension '74 alsopermits depression thereof manually to augment the counterclockwiserotation produced in the catch by the leaf spring 90, and the presenceof the extension portion permits the catch to be manually operated inthe event either springs 62 or 911 break.

The utilization of the leaf spring 90, and the simplified positioning ofthe carriage 1 12 makes the operation of the power unit by unskilledoperators feasible, andas the position of the carriage button 114 isreadily observable, the operator is able to immediately ascertain theposition of the catch, and the sequence of operation that will beproduced by the oscillation of the lever arm.

It is appreciated that various modifications to the inventive conceptmay be apparent to those skilled in the art without departing from thespirit and scope of the invention.

I claim:

1. A release mechanism for a ratchet-type power unit wherein the powerunit includes a rotatable drum having ratchet teeth defined thereon, atension member wound on the drum, a movable pawl selectively engagingthe drum teeth to prevent drum rotation in an unwinding direction and alever arm mounted for pivotal movement about the axis of drum rotationcomprising, in combination, a catch pivotally mounted upon the lever armabout a pivot axis, said catch including a ratchet tooth engageableabutment surface radially spaced from said pivot axis adapted to bealigned with and engage the drum ratchet teeth at a first pivot positionof said catch and adapted to clear the ratchet teeth at a second pivotposition of said catch, a first resilient spring mounted on said leverarm imposing a biasing force on said catch about said pivot axis biasingsaid abutment and catch toward said first pivot position, a secondresilient spring mounted on said lever arm selectively imposing abiasing force on said catch greater and opposite to that of said firstresilient spring for selectively biasing said catch to said second pivotposition, and control means movably mounted on the lever arm forselectively rendering said second resilient spring operative andinoperative.

2. In a release mechanism for a ratchet-type power unit as in claim 1wherein said control means includes a spring compressor movable betweena second position engageable with said second resilient spring to compress said second resilient spring and bias said catch to said secondpivot position and a first position out of engagement with said secondresilient spring.

3. In a release mechanism for a ratchet-type power unit as in claim 1wherein said control means includes a guide mounted on the lever arm, aspring compressor slidably mounted on said guide movable between asecond position engageable with said second resilient spring to compresssaid second resilient spring and bias said catch to said second pivotposition and a first position out of engagement with said secondresilient spring.

4. In a release mechanism for a ratchet-type power unit as in claim 1, aguide plate mounted on the lever arm adjacent said catch, a slot definedin said guide plate transversely disposed to said catch pivot axis, amanually operated carriage element slidably mounted within said slot, aspring compressor mounted upon said carriage, said carriage beingmovable in said slot between a second position wherein said compressorcompresses said second resilient spring to bias said catch to saidsecond pivot position and a first position wherein said compressor isout of engagement with said second resilient spring.

5. In a release mechanism for a ratchet-type power unit as in claim 4wherein said guide plate includes a first side readily accessible to thepower unit operator and a second side disposed toward said catch, saidcarriage element including a finger engageable button disposed adjacentsaid guide plate first side, said spring compressor being disposedadjacent said guide plate second side.

6. In a release mechanism for a ratchet-type power unit as in claim 1wherein said second resilient spring comprises a leaf spring having afree end extending toward said control means and an anchored end affixedto said catch, said leaf spring1 extending around said catch pivot axisfrom said anc ored end prior to defining said free end.

7. A release mechanism for a ratchet-type power unit wherein the powerunit includes a rotatable drum having ratchet teeth defined therein, atension member wound on the drum, a movable pawl selectively engagingthe drum teeth to prevent drum rotation in an unwinding direction and alever arm mounted for pivotal movement about the axis of drum rotationcomprising, in combination, a catch pivotally mounted upon the lever armabout a pivot axis, said catch including a hub, a finger extending fromsaid hub having an end adapted to be aligned with and engage the ratchetteeth at a first pivot position of said catch and adapted to clear theratchet teeth at a second pivot position of said catch, an extensionextending from said hub in a direction away from said finger having amanually operable outer end extending from the lever arm, a first springimposing a biasing force on said catch about said pivot axis biasingsaid catch toward said first pivot position, a leaf spring mounted onsaid catch having a free end radially spaced from said hub and ananchored end fixed to said catch, a manually operated carriage slidablymounted on the lever arm for movement toward and away from said leafspring free end and a spring compressor defined on said carriage adaptedto selectively engage said leaf spring free end to deform said springfree end and bias said catch to said second pivot position.

8. In a release mechanism for a ratchet-type power unit as in claim 7, aguide plate mounted upon the lever arm, an elongated slot defined insaid guide plate, said carriage being slidably mounted within said slot.

9. In a release mechanism for a ratchet-type power unit as in claim 8,said leaf spring free end being of an elongated configurationsubstantially perpendicularly related to said catch pivot axis andincluding a first portion extending away from said guide plate and asecond portion extending toward said guide plate, said slot being inalignment with and disposed adjacent said leaf spring elongated freeend, said spring compressor engaging said free end second portion uponsaid carriage being aligned therewith and said free end first portionclearing said spring compressor upon said carriage being alignedtherewith.

10. In a release mechanism for a ratchet-type power unit as in claim 7wherein said catch extension includes a first side disposed toward saidcarriage and a second slide disposed away from said carriage, fasteningmeans fastening said leaf spring anchored end to said extension secondside, said leaf spring free end extending about said catch hub and beingdisposed adjacent said first side and toward said carriage.

fl k

1. A release mechanism for a ratchet-type power unit wherein the powerunit includes a rotatable drum having ratchet teeth defined thereon, atension member wound on the drum, a movable pawl selectively engagingthe drum teeth to prevent drum rotation in an unwinding direction and alever arm mounted for pivotal movement about the axis of drum rotationcomprising, in combination, a catch pivotally mounted upon the lever armabout a pivot axis, said catch including a ratchet tooth engageableabutment surface radially spaced from said pivot axis adapted to bealigned with and engage the drum ratchet teeth at a first pivot positionof said catch and adapted to clear the ratchet teeth at a second pivotposition of said catch, a first resilient spring mounted on said leverarm imposing a biasing force on said catch about said pivot axis biasingsaid abutment and catch toward said first pivot position, a secondresilient spring mounted on said lever arm selectively imposing abiasing force on said catch greater and opposite to that of said firstresilient spring for selectively biasing said catch to said second pivotposition, and control means movably mounted on the lever arm forselectively rendering said second resilient spring operative andinoperative.
 2. In a release mechanism for a ratchet-type power unit asin claim 1 wherein said control means includes a spring compressormovable between a second position engageable with said second resilientspring to compress said second resilient spring and bias said catch tosaid second pivot position and a first position out of engagement withsaid second resilient spring.
 3. In a release mechanism for aratchet-type power unit as in claim 1 wherein said control meansincludes a guide mounted on the lever arm, a spring compressor slidablymounted on said guide movable between a second position engageable withsaid second resilient spring to compress said second resilient springand bias said catch to said second pivot position and a first positionout of engagement with said second resilient spring.
 4. In a releasemechanism for a ratchet-type power unit as in claim 1, a guide platemounted on the lever arm adjacent said catch, a slot defined in saidguide plate transversely disposed to said catch pivot axis, a manuallyoperated carriage element slidably mounted within said slot, a springcompressor mounted upon said carriage, said carrIage being movable insaid slot between a second position wherein said compressor compressessaid second resilient spring to bias said catch to said second pivotposition and a first position wherein said compressor is out ofengagement with said second resilient spring.
 5. In a release mechanismfor a ratchet-type power unit as in claim 4 wherein said guide plateincludes a first side readily accessible to the power unit operator anda second side disposed toward said catch, said carriage elementincluding a finger engageable button disposed adjacent said guide platefirst side, said spring compressor being disposed adjacent said guideplate second side.
 6. In a release mechanism for a ratchet-type powerunit as in claim 1 wherein said second resilient spring comprises a leafspring having a free end extending toward said control means and ananchored end affixed to said catch, said leaf spring extending aroundsaid catch pivot axis from said anchored end prior to defining said freeend.
 7. A release mechanism for a ratchet-type power unit wherein thepower unit includes a rotatable drum having ratchet teeth definedtherein, a tension member wound on the drum, a movable pawl selectivelyengaging the drum teeth to prevent drum rotation in an unwindingdirection and a lever arm mounted for pivotal movement about the axis ofdrum rotation comprising, in combination, a catch pivotally mounted uponthe lever arm about a pivot axis, said catch including a hub, a fingerextending from said hub having an end adapted to be aligned with andengage the ratchet teeth at a first pivot position of said catch andadapted to clear the ratchet teeth at a second pivot position of saidcatch, an extension extending from said hub in a direction away fromsaid finger having a manually operable outer end extending from thelever arm, a first spring imposing a biasing force on said catch aboutsaid pivot axis biasing said catch toward said first pivot position, aleaf spring mounted on said catch having a free end radially spaced fromsaid hub and an anchored end fixed to said catch, a manually operatedcarriage slidably mounted on the lever arm for movement toward and awayfrom said leaf spring free end and a spring compressor defined on saidcarriage adapted to selectively engage said leaf spring free end todeform said spring free end and bias said catch to said second pivotposition.
 8. In a release mechanism for a ratchet-type power unit as inclaim 7, a guide plate mounted upon the lever arm, an elongated slotdefined in said guide plate, said carriage being slidably mounted withinsaid slot.
 9. In a release mechanism for a ratchet-type power unit as inclaim 8, said leaf spring free end being of an elongated configurationsubstantially perpendicularly related to said catch pivot axis andincluding a first portion extending away from said guide plate and asecond portion extending toward said guide plate, said slot being inalignment with and disposed adjacent said leaf spring elongated freeend, said spring compressor engaging said free end second portion uponsaid carriage being aligned therewith and said free end first portionclearing said spring compressor upon said carriage being alignedtherewith.
 10. In a release mechanism for a ratchet-type power unit asin claim 7 wherein said catch extension includes a first side disposedtoward said carriage and a second slide disposed away from saidcarriage, fastening means fastening said leaf spring anchored end tosaid extension second side, said leaf spring free end extending aboutsaid catch hub and being disposed adjacent said first side and towardsaid carriage.